Intrinsic mechanisms for generating diversity are important for survival of bacterial populations in the dynamically changing environmental conditions present in nature. However, in the controlled environment of the laboratory, these mechanisms can lead to unwanted genotypic and phenotypic alterations and the spontaneous genetic modification of an established production strain or a clone library is generally highly undesirable.
Escherichia coli (E. coli) is a universal cloning host and is the most common organism used in the production of proteins, metabolites and secondary metabolites in both research and industry. Several modifications have been made to improve the performance of E. coli hosts in these settings all of which follow the basic principle of streamlining metabolic pathways for the increased production of a given biomaterial coupled with reduction of unwanted byproducts. Along these lines, a variety of nonessential genes have been removed from an E. coli background to form viable reduced genome E. coli strains with little or no significant reduction in growth.
Although these reduced genome bacteria have proved beneficial in many respects, some genes, in their functional forms, remain difficult or impossible to clone in bacterial vectors even in reduced genome bacteria. Accordingly, there is a need for stable bacterial hosts with very low mutation rates in which such genes could be cloned.